Chapter 13 Support and Movement

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Why do Organisms need Skeletons?

• enable organisms to support and carry weight of
  their bodies and that structure involved in
  vertebrates is skeleton
• aquatic animals receive some lift from
  surrounding water called buoyancy

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• support is more important to terrestrial animals
  since they are under the influence of gravity,
  without support, they will collapse

• ALL vertebrates have an endoskeleton which means
  their bones are inside the body
• the bones form a supporting framework which
  offers a firm base for muscle attachment

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Skeletal Tissues

• endoskeleton of mammal is made up of bones and
  cartilage

• Structure of Bone
• consist of living cells surrounded
  by non-living mineral materials
  which are mainly calcium
  phosphate and carbonate,
  organic matter and water

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• blood vessels and nerves run through bone tissue
  to supply oxygen and food for bones to develop
  and grow
• outer part of a bone is compact bone which is
  hard and dense and consists of calcium phosphate
  and carbonate

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• both ends are filled with loose
  spongy bone which contains many small cavities
  filled with red bone marrow

• red blood cells and white blood cells are made in
  red bone marrow
• inner part of bone is a central cavity which is
  hollow and filled with yellow bone marrow
• yellow bone marrow is a kind of fatty tissue

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Investigation13.1
To find out How the Chemical Components of Bone
Affects its Properties
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Can you bend the bone after acid treatment ?
Ans Yes.
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What effect does the acid have on the bone ?
Ans It dissolves away calcium salt, cause bone
to lose its strength and rigidity.
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What is the purpose of heating the bone in a
strong Bunsen flame ?
Ans It is used to burn away the organic
substance of bone.
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Describe the nature of bone after strong heating.
Ans The bone becomes brittle.
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Structure of Cartilage

• cartilage is the main substance supporting
  animal body during the
  embryonic stage
• cartilage will generally replaced
  by
  bones as animals grow
• all composed of living cells
  
  so it is able to grow and repair
• softer than bone and found
  on two ends of
  bones

structure of cartilage
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Functions of Cartilage

• cushion-like and acts as a shock-absorber
• reduces friction between two bones during
  movement
• prevent wearing of bones
• cartilage are also found in cartilage in the
  pinna of ears and in the end of nose to give
  shape of the organs

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General Plan of Mammalian Skeleton

• skeleton of a mammal is divided into two main
  parts
• Axial Skeleton
• - lies in the centre of the body
• - include skull, vertebral column, ribs
  and sternum

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• Appendicular Skeleton

- lies on either side of the body - include
pectoral girdles, pelvic girdles and limb bones
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Two parts of Skeleton
Appendicular skeleton
Axial skeleton
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Functions of Skeleton

• Support and Maintenance of Body Shape
• skeleton holds body upright and gives animal
  shape and form
• provide a framework for tissues and organs

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Attachment of Muscles for Movement

• muscles are attached across joints to bone
  surfaces
• with alternate contraction and relaxation of
  muscles, body can move

• Protection of Internal Organs
• lungs and heart are protected by rib cage
• spinal cord is protected by vertebral column

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Production of Blood Cells

• red blood cells and white blood cells are made by
  red bone marrow of certain long bones

• Storage
• yellow marrow stores fat
• compact bone tissue stores calcium and phosphorus

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Joints

• joint is formed wherever two or more bones meet
• two types of joints immovable and movable joints
• movable joints which allow a lot of movement is
  synovial joints examples of synovial joints
  elbow joint and shoulder joint

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Joints - Hinge Joint

• movement in one plane only
• found at knee and elbow

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Joints - Ball and Socket Joint

• allow movement in three planes and in all
  directions
• found at shoulder and hip

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Ligament

• fibrous tissue found at movable joint to hold
  bones together
• tough and strong
• prevent dislocation of joint
  during movement

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Structure of Synovial Joint

• beneath ligament is synovial membrane which
  secretes synovial fluid into synovial cavity
• synovial fluid serves
  as
  lubricant so
  movement of bones
  
  are friction-free

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• ends of bones are covered with articular cartilage

• it is softer and can act as shock-absorber to
  protect bones at the joint
• it is also used to minimize friction between
  bones and to ensure bone surfaces will not be
  worn away when bones move against one another

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Muscles

• muscles are attached to bone surface
• bones in mammals are joined to form a lever
  system
• force in a lever comes from muscle contraction
  which energy results from respiration but energy
  does not require when muscle relaxes

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• skeletal muscle

- muscles attached to bone surface - voluntary,
under conscious control - gives
powerful contraction and become
thicker and shorter so
movement of bones results
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- fatigue results when it contracts too long,
as lactic acid accumulated in muscle cells due
to anaerobic respiration

• muscle contract

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Muscles and Skeleton

• muscles are attached to skeleton by tendon
• tendons are tough connective tissue, collagen

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• begins inside bone and penetrates deep into muscle

• cannot stretch
• insertion is the end of muscle attached to a
  movable bone during muscle contraction while
  origin is the end attached to a fixed bone during
  muscle contraction

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How is movement achieved?Movement of Forearm

• biceps and triceps are involved
• forearm bends when
  biceps contracts and
  triceps relaxes and it
  straightens when their
  roles exchanged

limb straightens
limb bends
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How is movement achieved?

• Biceps and triceps are antagonistic muscles
  involved in the movement of the forearm. They
  work in pairs and in opposing directions.

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• members in antagonistic pair are flexor and
  extensor

• flexor contracts to bend the limb while extensor
  straightens the limb when it contracts

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• biceps attach to its origin and insertion by two
  tendons while triceps attach to origin and
  insertion with three tendons

• contraction of biceps together with relaxation of
  triceps make forearm to move close to upper arm
  and vice versa for straightening of the limb

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Investigation13.4
To show the Action of Opposing Muscles by using a
Model of the Forelimb
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What parts of the forelimb are represented by the
two balloons, the screw between woods Y and Z and
the wood?
Ans The two balloons, the screw between woods Y
and Z and the wood represent triceps and biceps,
elbow joint and bones respectively.
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Which balloon represents the biceps? Which
represents the triceps?
Ans Balloon A represent triceps while balloon B
represents biceps.
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What happens to biceps and triceps as the forearm
is bent?
Ans As forearm is bent, biceps contracts and
becomes shorter and fatter and triceps relaxes
and becomes longer and thinner.
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Lever

• lever is a bar which is turned about a fixed
  point which is called fulcrum
• on one side of fulcrum is load and effort is
  applied on the other side. Force is transmitted
  along lever to the load
• e.g. elbow joint

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contraction of biceps (effort)
elbow joint (fulcrum)
hand (load)

• Hinge joints act as the fulcrum
• Lower arm and hand act as load
• Contraction of biceps creates the effort to lift
  up the arm and bends elbow

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Other Types of Lever System in our Body

• Standing on tiptoes

Second order lever system
Nodding of head
first order lever system
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Importance of Support in Plants

• display leaves in the best position to absorb
  enough light for photosynthesis
• lift flowers to higher positions so fruits and
  seeds can be dispersed over a wide area. This
  helps species to propagate to new area

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Support
mainly provided by turgidity of cells and
rigidity of xylem
Turgidity of Cells

• mainly support young plants
  and non-woody parts of a dicotyledonous
  plant which the
  cells are thin-walled

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• thin-walled cells absorb water by osmosis and
  become turgid

• turgid cells then press against each other and
  keep the whole stem upright
• if cells lose water and become flaccid, plant
  will wilt and becomes soft and droopy

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• on hot days, when transpiration proceeds faster
  than water absorption

In this case, transpiration is faster than
absorption of water
wilting occurs
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Rigidity of Xylem

• When dicotyledonous plant grows
  older, more secondary xylem tissue
  formed by vascular cambium, plant
  becomes woody

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• xylem vessels support plant mechanically as
  they have thick walls containing lignin

• lignified cells give strength and rigidity to
  plant

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